This invention relates generally to spring assemblies for use in mattresses, spring-upholstered furniture and the like and, more particularly, to a pocketed coil spring assembly and an associated method of manufacturing such an assembly.
A well known type of bedding or seating product comprises a pocketed spring assembly which includes a number of discrete coil springs, each of which is enclosed in a fabric pocket in a length of folded fabric material. Longitudinal axes of the coil springs are generally parallel with one another so that the top and bottom end turns of the coil springs define top and bottom faces of the pocketed spring assembly. A row of such pocketed springs is known in the industry as a string of pocketed springs. A bedding or seating product can be fabricated from such strings of pocketed springs by binding or adhering the individual rows or strings of pocketed springs together to form a pocketed spring assembly. The pocketed spring assembly may then be padded and encased in an upholstered covering. U.S. Pat. No. 6,143,122 discloses one such method of adhesively bonding strings of pocketed springs together to form a pocketed spring assembly.
Mattresses and similar articles constructed of pocketed spring assemblies are often considered a high-end product because of the added benefits and features of the pocketed coil springs. Typically, within a string of springs, opposite plies of fabric are welded, glued, sewn, or otherwise secured together between adjacent coil springs with a generally vertically oriented seam or line of attachment. At the ends of the string of springs, an outermost seam prevents the outermost coil springs from falling out of the string of springs. A pocketed spring assembly made by joining multiple such strings of pocketed springs creates what is considered in the industry as a xe2x80x9chigh densityxe2x80x9d pocketed spring assembly due to the large number of pocketed coil springs in the spring assembly. Within each of the strings of pocketed springs, there is little space between adjacent pocketed coil springs.
One alternative to this construction of a string of springs is to manufacture a string of pocketed springs in which fewer coil springs are used in the string. One method of doing this is to sew, weld, or otherwise secure together opposed plies of fabric along two spaced, generally vertically oriented seams between adjacent pocketed coil springs. U.S. Pat. No. 2,048,979 discloses this type of construction of a string of pocketed springs. The effect of joining multiple strings of springs of this type is to reduce the number of coil springs in the pocketed spring assembly, thereby creating a xe2x80x9clow densityxe2x80x9d pocketed spring assembly. One advantage of a xe2x80x9clow densityxe2x80x9d pocketed spring assembly is that fewer springs are required than in a conventional xe2x80x9chigh densityxe2x80x9d pocketed spring assembly. One drawback to such a xe2x80x9clow densityxe2x80x9d pocketed spring assembly is that due to the fabric between adjacent pocketed coil springs, one or more of the strings of springs of the assembly may collapse in a longitudinal direction, adjacent pocketed springs moving together. Therefore, there is a need for some additional structure to stabilize the strings of springs of the xe2x80x9clow densityxe2x80x9d pocketed spring assembly and prevent them from collapsing inwardly.
U.S. Pat. No. 2,048,979 discloses one method of preventing the strings of springs of a xe2x80x9clow densityxe2x80x9d pocketed spring assembly from collapsing. U.S. Pat. No. 2,048,979 discloses wires in both the top and bottom surfaces of the pocketed spring assembly which are bent around the end turns of the pocketed coil springs to prevent the strings of springs from collapsing. One drawback to this pocketed spring assembly is that it is expensive to manufacture due to the necessary manipulation or bending of the wires.
Therefore, there is a need for a xe2x80x9clow densityxe2x80x9d pocketed spring assembly, i.e. made of strings of pocketed springs in which more than one seam separates adjacent pocketed springs, which is structurally rigid and will not collapse. There is a further need for a pocketed coil spring assembly which may be manufactured less expensively than heretofore known pocketed spring assemblies, yet is stable. Additionally, there is a need for a xe2x80x9clow densityxe2x80x9d pocketed spring assembly which may be manufactured without the higher manufacturing costs, production difficulties, and inefficiencies associated with known xe2x80x9clow densityxe2x80x9d pocketed spring assemblies.
The invention of this application which accomplishes these and other objectives comprises a bedding or seating product comprising a pocketed spring assembly, padding and an upholstered covering encasing the pocketed spring assembly and padding.
The pocketed spring assembly comprises a plurality of parallel strings of springs joined to each other, each of the strings of springs comprising a row of interconnected fabric pockets. Each of the pockets contains at least one spring encased in fabric. The springs are preferably coil springs but may be other types of springs. In the event coil springs are used, each of the coil springs has a central axis, an upper end turn, a lower end turn, and a plurality of central convolutions between the end turns. Preferably, each string of springs is made of one piece of fabric folded and welded into a plurality of pockets, each of the pockets containing at least one spring. Opposed plies of the string of springs may be joined by sewing, gluing, sonic welding or any other method known in the art.
Each string of springs is contained within a longitudinally extending row of integrally connected closed fabric pockets, each pocket of which contains one helically coiled wire compression spring having its axis disposed transversely of the row. The pockets are defined between two overlapped plies of fabric by spaced transverse lines of attachment or seams of the plies to one another and by connection of the plies together along a longitudinally extending line of attachment or seam.
In one preferred embodiment of the present invention, a spacer strip extends between and is secured to the top surface of each row of interconnected pockets of each string of springs. Therefore, each string of springs has a single spacer strip extending between the interconnected pockets of the string of springs, intersecting the axes of the coil springs. The spacer strips may be secured to the fabric pockets by gluing, welding or any other suitable method. Thus, each spacer strip extends longitudinally, parallel its associated string of springs. Each spacer strip is preferably made of plastic but may be made of any suitable material.
In another preferred embodiment, spacer strips are secured to selected strings of springs, for example, every other string of springs. A spacer strip may be secured to the top or bottom surface of the string of springs, or both the top and bottom surfaces of the strings of springs. More than one spacer strip per string of springs is also contemplated by the present invention.
In yet another preferred embodiment of the present invention, at least one scrim sheet may be secured to the strings of springs to prevent the strings of springs from collapsing longitudinally. In this embodiment, at least one scrim sheet is glued, ultasonically welded or otherwise secured to the fabric of the strings of springs. The scrim sheet or sheets may be secured to each string of springs or only select strings of springs.
In any of the preferred embodiments described above, the strings of springs may be oriented transversely or longitudinally of the bedding or seating product.
In one method of manufacturing a bedding or seating product in accordance with the present invention, the pockets of the strings of springs are filled with at least one spring before being closed. Preferably, each pocket is closed immediately after the spring is inserted therein. In accordance with the practice of this invention, some, if not all, of the adjacent pockets of a string of pocketed springs are separated by more than one line of attachment so as to create a so-called xe2x80x9clow densityxe2x80x9d string of pocketed springs. The finished string of xe2x80x9clow densityxe2x80x9d pocketed springs is then joined to adjacent finished strings of springs to form a pocketed spring assembly. In one embodiment of the present invention, at least one spacer strip is then secured along the length of each of the strings of springs to prevent its collapse. Alternatively, the spacer strips can be secured to the strings of springs prior to joining adjacent strings of springs together. Either way, once the strings of springs have been attached to each other, thereby forming a pocketed spring assembly, the pocketed spring assembly is covered with padding and encased in a fabric covering.
These and other objects and advantages of the invention will be more readily apparent from following description of the drawings in which: